Hi Folks

  

The reason I am e mailing you is I just found a very interesting SAE paper written by some of the Honda motorcycle engineers back in 1970, one by name of Shaon Yagi. A great paper overall on what design features of an engine are of most importance in production of power.  But, one part of the paper talked about tuning by Pulse induction tuning!  Well, that got my attention!  I was surprised and stunned to find out that  the equations that Yagi shows and my DIE equations are equivalents! 

 

 There are some differences, but I think they are related to how the pulses are used (he only uses the "A" pulse formed by closing of the intake valve) and his is for four stroke engines and of course the cycle timing of the rotary on intake is like a two stroke timing wise.  So I think those differences account for most of the differences in our equations.

 

His equations clearly show that port timing plays a crucial role in pulse tuning as did my independent derivation for the twin rotor. This relevation was probably the most significant in my findings as well.  I have attached the page addressing "Pluse Tuning" from the paper for those of you who may be interested.

 

In any case, referencing page 10, his first equation for "t" and my "Ta" equations are amost identical, clearly showing that port timing places a crucial role in pulse tuning - be it 4 stroke piston engine or rotary.

 

I found his equation regarding "Pulse Tuning" (same as DIE) on page 10.

 

 Yagi's equation t = (f^*/360)*(60/Ne)  Where Ne is shaft rpm and f^{*  is the degree of crankshaft rotation from inlet valve closure to TDC during inlet operation of the next succeeding cycle.}

The formula seemed vaguely familiar, then I realized if I revised it slightly I could express it as:

t = f^*/(360*(Ne/60)) and the reason for the familarity was readily apparent. Recall my equation for Time Available Ta?  Well with my Ad =f^*    the two equations are equivalent

My Ta = Ad/(360*(rpm/60)) or  Yagi's  t = f^*/(360*(rpm/60)) where Ne = RPM

Ta = Ad/Ars  Where Ad = Angular Difference and Ars = Angular rotational speed of the E shaft

Well

Ars  Angular Rotation Speed (Deg/Sec) = 360*(RPM/60)

which of course in Yagi's equation is the (1/360)*(60/Ne) factor.

So basically my Ta = Ad/(360*(RPM/60) (where f^{*   is the equivalent of my Ad.)  and Yagi's equation are equivalent.}

His f^{*  and my Ad are a bit different, but I think that is because he is working on a 4 stroke and I on the rotary which acts like a 2 stroke in its induction cycle.  Also he is having the pulse return to the cylinder in time for the next induction cycle of that cylinder (sort of a round trip) and mine only goes one way from rotor to rotor.  Or perhaps its simply a different arrival point is required for returning the pulse to its generating cylinder just as it is about/begining to open rather than as it is closing (as is the second rotor's intake in the DIE analysis) is resonsible.}

^His  f^{*  = 180deg-IC,   IC = inlet valve closing angle expressed as ABDC.  My Ad = 90+IC-IO}

^{But, again I think its because he is "supercharging" the same cylinder the pulse came from (and using the "A" pulse instead of the "B" pulse).  So his interval is from closing to opening on the same cylinder and mine is from opening to closing on different cylinders/rotor.  Perhaps some of you folks can provide clarity on this point for a four stroke reciprocating engine.}

We also have the equivalent Tr (time required) with mine Tr = L/vp and his

t = 4*L/As   His As is my Vp (speed of sound).  The only thing I don't understand is why his time for the pulse to travel the length of the intake pipe is equal to 4*L instead of my 1*L.  It appears as though he is making his pulse travel 4 times the length of the intake manifold, but then its is not abolutely clear what his intake pipe length really is. It may have to do with a multiple bounce of pulses.  i.e. using every 4th pulse? or perhaps because there is the "rest" stroke on a 4 stoke cycle which the rotary does not have? Just not clear to me at this point, why the 4*L.

In any case, he eventually ends up with the equivalent of my parametric equation!

  I could hardly believe it!  Solving for Length of the manifold "L" in his equation

His was L =  As* f^* /gt4*(6*Ne)   wereas mine was L = Vp*(Ad)/6*RPM (or it could be reduced to that form) where my Ad = f^{*   and my Vp = his As  The gt factor in his equation is a pulse selection factor - do you want to tune by the first pulse in which case gt = 1 or perhaps a 2nd or 4th pulse in which case gt = 2,4, etc.  Since I was only concerned with the first pulse gt became 1 and isn't a factor in my equation.  But, I think it may indicate a point that some of you raised during the presentation (Finn?) that perhaps there are some DIE effect at mulitples of "L" if the pulse retains sufficient energy after several trips through the intake.}

^{The only thing that I can't explain about his equation is the factor or "4" for his Time required for the pulse to transverse the intake pipe.}

So, now more than ever, I know my orginal analysis is on solid ground. The only other difference is that he apparently does not address any pulse duration effect in his equation.  Perhaps this is not as critical when the pulse returns to the port that generates it?  Perhaps with the shorter L implied for the two rotor timing is more critical and the pulse duration must be accounted for? 

In any case,  its great to find independent confirmation for my derivations or at the very least, it clearly shows that Port timing is crucial in pulse tuning or DIE as I showed, but which some folks apparently still don't believe or understand.  Just thought you might like to know that the DIE analysis is on frimer ground than just based the quality of my derivation. 

Best Regards

Ed Anderson

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

 

Attachment: page10.jpeg 

(142K)